Synthetic grass surfaces typically comprise a synthetic surface from which extends tufts of simulated grass fibres of a plastic material. Sand is laid on the surface filling the spaces between the tufts so that the tufts remain substantially erect and produce a flat surface which provides a surface suitable for use as a recreational surface.
Typically synthetic grass is very durable. Sand normally collects at the bottom of the synthetic grass and grime, mould and mildew collects on external fibres of the synthetic grass leading to premature degradation and a reduction in performance.
Because the synthetic grass is porous whenever rain falls, dust and contaminants rise to the surface of the synthetic grass fibres leading to a degradation in surface quality and consequential problems for the sporting activity for which the synthetic grass is being used.
Sweeping a synthetic grass surface with a brush is normally ineffective because not all particulate material is moved and when it is moved, it tends to disperse in all directions. Brushing is generally ineffective in breaking up aggregated particulate matter and can in fact damage the fibres of the synthetic grass surface. Brushing does not remove dust and other contaminants, it merely redistributes these contaminants which are believed to be the main cause of aggregation of sand particles, the consequential compaction of fibres and the growth of algae and moss.
Moreover, to attempt to clean an entire tennis court using such a method in conjunction with a washing detergent would be extremely time consuming. Accordingly, there is a need for an apparatus which can effectively remove particulate material as well as organic material such as mould and mildew from deep within the synthetic grass.
In the past, cleaning a synthetic grass surface has been performed with high-pressure water. Cleaning in this manner is a very untidy process and usually requires the replacement of much of the sand and also a considerable amount of relevelling. Relevelling is difficult with wet sand and is a particularly laborious, time-consuming process.
Machines for cleaning synthetic grass surfaces are also known. The machines generally pass over the surface and have a front head attachment which blows high-pressure air against the ground surface to be cleaned. The head attachment has a shroud in which a plenum chamber is located and through which plenum chamber the high-pressure air passes against the ground surface. The pressurized air was dispersed onto the synthetic grass surface using a perforated drum which expelled air at a fixed angle onto the synthetic grass surface as the machine passed over the surface. The high-pressure air breaks up any dirt, debris, moss, caked sand, dust, and the like, and some separation of dust and sand is achieved by virtue of a powerful vacuum arrangement in the head attachment. The cleaned sand passes through the baffles and back onto the playing surface, while the dust, dirt, and the like passes through an outlet and into collection bags. Because the head attachment is not very efficient in separating dust from sand, much sand also passes into the collection bags and therefore the collection bags are arranged upwardly with a lower inlet such that the heavier sand passes back through the inlet and into a sand collecting chamber. An example of this apparatus is described in my earlier Australian patent no. 647607.
While this apparatus was satisfactory for some users, it was found that too much sand was being removed from the playing surface. The upward vertical collection bags were also quite dangerous as they were fully exposed and tended to flap in the wind. The apparatus was also not suitable for any cleaning other than separating dust from sand, and thus the apparatus was more or less limited to tennis courts.
I then developed an improved model of this apparatus in which a baffle was located within a shroud of the head attachment and above the plenum chamber, the baffle having a first leading portion joined to an inner wall of a leading portion of the shroud, and also having a trailing portion spaced inwardly from the trailing portion of the shroud. Accordingly, the baffle formed a torturous pathway for dust thrown up by the compressed air to pass through the outlet. This arrangement considerably improved the separation of dust and sand meaning that a minimum amount of sand passed through the outlet into the collection bags.
Again, while the cleaning achieved this apparatus performed was satisfactory, it was still found that too much sand was being removed from the playing surface. The machine also tended to flatten the synthetic grass fibres or force them to adopt a prone condition. This reduces the effectiveness of the cleaning performed and also the quality of the synthetic grass surface after cleaning.
It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.